1. Field of the Invention
The present invention relates to an actuation device for a cable-operated parking brake of a motor vehicle and which enables actuation of the parking brake selectively by muscular energy or with a motive power assist, the actuation device including a muscular energy-actuated member for actuating the parking brake, an auxiliary motor for actuating the parking brake, a brake cable tightening device, and a drive for actuating the brake cable tightening device and including, first and second drive elements connected, respectively, with the muscular energy-actuated member and the auxiliary motor, and a connection element for selectively connecting one of the first and second drive elements with the brake cable tightening device.
2. Description of the Prior Art
Actuation devices of the type described above, with which a parking brake can be selectively actuated either by muscular energy or by an auxiliary motor, in particular, an electric motor, find lately ever increasing application in motor vehicles for improving an operational comfort of motor vehicles. Actuation devices of this type are available in many different embodiments.
Besides relatively simple actuation devices, with which the parking brake is actuated, during a normal course of operation, by an electric auxiliary motor and only in case of an abnormal occurrence, with a conventional brake lever by applying a muscular energy thereto, there exist actuation devices with which the parking brake can be arbitrary actuated either with a conventional hand brake lever or a pedal by applying a muscular energy thereto, or with a switch-actuated electric auxiliary motor. One of such actuation devices for an arbitrary selection of the type of actuation of a parking brake is disclosed in German Publication DE-OS 32 10 402. In the disclosed actuation device, a force transmitting member, which transmits the force applied to the pivotal hand brake lever to a tightening element of the parking brake, is formed as a cable secured to the hand brake lever at a distance from the pivot axis of the hand brake lever. Besides, the cable is enveloped by an electromotor-driven friction wheel, with the electromotor being secured either to the hand brake lever or being secured on the vehicle body, separately from the hand brake lever. In this actuation device, the electromotor actuating switch is mounted on the hand brake lever. When the hand brake lever is pivoted, to apply the brake, upward, the electromotor is actuated and the friction wheel transmits a power-assist force, which is added to the actuation force applied to the hand brake lever, to the cable-shaped power transmitting member. Actuation of the parking brake only with the electromotor in not possible with this actuation device.
In another known actuation device for a motor vehicle parking brake, a hand brake lever, which pivots about a stationary axle and is retained in different pivotal position by a pawl, is connectable with a cable pulley which forms a tightening element for the cable and is supported on the same axle as the hand brake lever. A drive connects an electromotor with the cable pulley. For selectively actuating the hand brake either with the hand brake lever or with the electromotor, there is provided a manually-operated clutch which alternatively or selectively connects the cable pulley, which forms the brake cable tightening device, with either manually operated hand brake lever or with an auxiliary drive including the electromotor. This actuation device provides for both actuation of the parking brake only by muscular energy and actuation of the parking brake only by the electric motor. However, this known actuation device has increased dimensions because the hand brake lever, the tightening element, the switching clutch, and a drive pinion of the electromotor-operated drive need be arranged in a row. Therefore, this actuation device can be fitted in a motor vehicle with a pedal-operated parking brake only with great difficulties and with significant additional expenses.
Accordingly, an object of the present invention is an actuation device for a motor vehicle parking brake which would insure a selective actuation of the parking brake either by muscular energy or with electromotive energy assist, while requiring a smaller mounting space in a motor vehicle.
Another object of the present invention is an actuation device of the above-described type which is characterized by reduced technical expenses.